Large area sensing is critical for a variety of military, ecological and commercial interests and has historically been served through the use of centralized long-range sensors. However, rapid improvements in miniaturization of electronic systems have significantly improved the capabilities of small sensor devices. These micro-sensors have the potential to create “large N” distributed networks with advantages in operational adaptability, non-traditional sensing modalities that are only possible with close proximity, increased sensitivity and knowledge extraction through networked intelligence.
While distributed network systems have remarkable promise, their realistic use is limited by risks associated with their accumulation in the environment, detection and defeat, and exploitation due to inability to maintain positive control (unlike centralized long-range sensors).
The phrase “transient electronics” refers to a relatively new family of electronic devices that disappear (disaggregate and disperse) within a set period of time, making them ideally suited for distributed network systems. Conventional transient electronic systems typically rely on the use of soluble substrates and electronic materials (such as silk). When placed into solvent (typically water), these conventional substrates and electronics slowly dissolve into solution. As such, a distributed network system made up of conventional transient electronic devices can be expected to “disappear” over a relatively short amount of time (e.g., after periodic rainfall).
Although the conventional transient electronic approaches achieve the goal of causing the electronics to “disappear” after use, the long dissolution period required to achieve complete disaggregation and dispersal make the conventional approaches unfit for discrete (e.g., military) applications that require rapid and complete disaggregation upon command. Moreover, the conventional approaches utilize materials that are not compatible with existing integrated circuit fabrication and assembly techniques, requiring the development of new IC fabrication processes at significant cost.
Interposers are well-known electrical interfaces in the context of semiconductor device packaging, and are typically disposed between an IC die (chip) and a standardized semiconductor package structure, such as a ball-grid array (BGA) package or a pin-grid array (PGA) package. Interposers typically include a flat insulator substrate (e.g., either a rigid insulator such as FR4, or a flexible insulator such as polyimide) through which multiple metal conductors extend between corresponding contact structures (points) that are disposed in two different patterns on opposing substrate surfaces. That is, a first set of contact points disposed on one side of the interposer substrate are formed in a pattern that matches corresponding contact pads on the IC die to facilitate IC-to-interposer connection (e.g., by way of surface mounting techniques), and a second set of contact points on the opposing side of the interposer are arranged in a second (different) pattern that matches corresponding contact structures disposed on an inside surface of the host package to facilitate surface mounting of the interposer to the host package. The metal conductors pass through the interposer substrate to provide signal paths between corresponding contact structures of the first and second sets. With this arrangement, when the host package structure is subsequently connected, e.g., to the printed circuit board (PCB) of an electrical system, the interposer facilitates passing signals between the IC die(s) and the electrical system by way of the I/O pins/balls of the host package.
Interposers were originally typically utilized to reroute IC die connections to corresponding contact points on standard package structures, but more recently serve other purposes as well. For example, as advances in semiconductor fabrication facilitate smaller IC die having correspondingly finer pitched IC die contact pads, interposers are also utilized to spread the finely spaced IC die contact points to wider pitches that are more compatible with conventional package structures. In this case, the interposer includes first contact points arranged in a finely pitched (first) pattern on one surface, and second contact points arranged in a widely pitched (second) pattern on the opposing surface, with conductive metal vias and traces extending through the substrate and along the opposing surfaces to provide electrical signal paths between associated first and second contact points. In addition to spreading finely spaced IC die contact points to wider pitches, interposers are being used to secure two or more die into a single package structure.
What is needed is a transient electronic package assembly that is compatible with existing IC fabrication techniques, and achieves sufficiently complete, on-command disaggregation of IC die disposed thereon to provide both security and anti-tampering protection by way of preventing access to the intact integrated circuit implemented on the IC die.